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Problems to send data over Modbus TCP

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Hi, I'm using a Samba 3.5 with ethernet card to send data to scada system.  With test purposes I'm trying to send a discrete input MB 0 in response to the read digital input command (0x02) with the following instruction:


But in the test software (Simply Modbus TCP Client) I can't see the value of MB0.

Trying to find the answer, I tested sending the MI10 value in response to read holding registers command, but It doesn't work neither.


I'm using the modbus TCP initial setup from the examples and the webinars, and I can see the connection in the Samba, but I can't send the data.

I don't know if I'm missing something, this is my very first time with Unitronics  modbus TCP.  I really appreciate any help or suggestion to put me in the right way.




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If your PLC is slave, it answers for SCADA request.

So, you do not need to send replay from Ladder.

You can look MODBUS IP examples for Slave and Master in Examples directory, where you installed VisiLogic.

C:\Program Files (x86)\Unitronics\Unitronics VisiLogic_C\Examples\Version 900\Project examples\Communications\Ethernet\Ethernet MODBUS IP\

Or from "Menu->Help->Examples->Version 900\Project examples\Communications\Ethernet\Ethernet MODBUS IP\

In your case PLC is Slave.

You have to configure is as Slave and everything should work.

Commands you use are for Master PLC.

Other error is that you use Normal Closed contact "Function in Progress".

This mean that you send a lot of MODBUS messages to network.

Follow MODBUS IP example for Slave to make MODBUS IP working.


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